Chemo-mechanical Characterization of Bitumen Binders with the Same Continuous PG–Grade
Chemo-mechanical analysis tools were used to provide plausible reasons behind different binder properties that are not well captured by the conventional Superpave PG-grading system. In this study, six binders were divided in two groups based on their continuous PG-grades. The binder matrix includes: two SBS modified binders, one air blown bitumen, one bitumen with high wax content and two other unique binder blends. Although the binders in each group have the same continuous PG-grades based on AASHTO M320, they exhibit very different low-temperature performance based on the binder relaxation ΔTc index, and they have different upper PG performance according to MSCR testing and AASHTO MP19, which takes into account both traffic load and climate conditions. Based on the results, high apparent molecular weight waxes appear to lead to poor low-temperature cracking and lower molecular weight waxes lead to poor rutting performance. Meanwhile incompatible polymer modification seems to lead to poor rutting and cracking performance relative to unmodified binders or even air blown binder.
KeywordsBinder waxes Polymer compatibility SAR-AD Waxphaltene Determinator 4-mm DSR MSCR Glass transition Crystallizable fractions
The authors would like to acknowledge AIRC-1st Iteration members (Surfax, Repsol, Husky, BRRC, IFSTTAR, Eiffage, Eurovia, and WRI). The authors would also like to acknowledge P. Coles for rheological testing, J. Forney for DSC measurements, J. Loveridge and J. Rovani for SAR-AD analysis, N. Bolton for running FT-IR, and R. Boysen for performing SEC analysis.
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